A government audit of a renewable energy scheme, ordered in the wake of the RHI scandal, has yet to complete, it can be revealed.

And an MLA who called for the audit described the lack of progress as "worrying" saying its completion should a "major priority" for Stormont officials.

As one of his last acts as Economy Minister Simon Hamilton ordered a review of all the Department for the Economy's renewable schemes in light of the maladministration of the RHI scheme.

Lack of cost controls in the Renewable Heat incentive meant it went over budget leaving the Northern Ireland taxpayer facing a possible £700million bill.

There has also been lengthly and protracted legal battles over the department's attempts to curb costs. In one judicial review all costs were awarded against the department.

Speaking in the Assembly last year Mr Hamilton said that while there was no evidence of problems with other schemes, he could understand there being concerns given the RHI errors.

"If mistakes have been made in one renewable scheme, that could be the case in others as well. I have ensured that some concerns that have already been brought to my attention have been investigated, but I will formalise that by initiating an audit of all renewable schemes," he said.

The minister also established a "strategic energy team" within his department which would draw on experience from the public and private sectors in order to "improve the quality" of advice to the minister.

However, one year on from that statement, the Department of Economy has said there was only the one other renewable scheme which required an audit.

It is the Northern Ireland Renewables Obligation (NIRO) which looks to encourage people and organisations to take up renewable electricity generation rather than relying on traditional means. Like the RHI scheme is operates in tandem with similar schemes in Britain.

Given predictions Northern Ireland will require more electricity than it will generate by 2021, there is a growing urgency in government to find new ways to supply the grid.

An audit of NIRO has not yet been completed, the Department for the Economy confirmed. It would not say when that audit began or when it was likely to complete.

Ulster Unionist MLA Steve Aiken, who as chair of the Stormont Economy committee pushed for an audit of the renewable scheme.

He said there were already questions over NIRO which concerns energy generation from the likes of wind and wave power. According to the MLA it had recommended more wind farms should be built than what the current Northern Ireland electricity network could handle.

"Given the obvious problem there is with energy schemes and how they work there should be an urgency to have them audited," he told the Belfast Telegraph.

"The department is clearly not fit for purpose, this is very worrying," he told the Belfast Telegraph.

"This should not just be a priority for the department, it should be its major priority."

He continued: "The RHI scheme, as the inquiry has been hearing, was a scheme which replaced a scheme that was itself a disaster and look how that turned out.

"It should be a major priority full stop for the department to do something and have this audit completed.

"The department has no credibility and to discover they have not conducted an audit of NIRO at at time when energy supply in Northern Ireland is a real issue is incredible."

A Department for Economy spokesperson said: “The Department has only one other major renewable scheme which is the Northern Ireland Renewables Obligation (NIRO). Work is currently ongoing to review this scheme. While this work is ongoing it wouldn’t be appropriate to comment further.”

The RHI scheme was initially set up by DUP leader Arlene Foster during her time as Enterprise Minister. An inquiry, chair by retried judge Sir Patrick Coghlin is ongoing to investigate the scheme and how it went wrong.